Carbon filtering is a method of filtering that uses a bed of
activated carbon
Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that increase the surface area avail ...
to remove impurities from a fluid using
adsorption.
Mechanism
Carbon filtering works by
adsorption, in which pollutants in the fluid to be treated are trapped inside the pore structure of a carbon substrate. The substrate is made of many carbon granules, each of which is itself highly
porous. As a result, the substrate has a large surface area within which contaminants can be trapped. Activated carbon is typically used in filters, as it has been treated to have a much higher surface area than non treated carbon. One gram of activated carbon has a surface area in excess of 3,000 m
2 (32,000 sq ft).
Common uses
Carbon filtering is commonly used for
water purification,
air filtering and industrial gas processing, for example the removal of
siloxanes and
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
from
biogas. It is also used in a number of other applications, including respirator masks, the purification of
sugarcane
Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with ...
, some methods of coffee
decaffeination, and in the recovery of precious metals, especially gold. It is also used in
cigarette filters and in the
EVAP used in cars.
When filtering water, charcoal carbon filters are most effective at removing chlorine, particles such as sediment,
volatile organic compounds (VOCs), taste and odor. They are not effective at removing minerals, salts, and dissolved inorganic substances.
Specifications
Each carbon filter is typically given a ''micron rating'' that specifies the size of particle which the filter can remove from a fluid. Typical particle sizes which can be removed by carbon filters range from 0.5 to 50 μm. The efficacy of a carbon filter depends not only on its particle size, but also on the rate of flow of fluid through the filter. For example, if a fluid is allowed to flow through the filter at a slower rate, the contaminants will be exposed to the filter media for a longer amount of time, which will tend to result in fewer impurities.
See also
*
Water filter
*
List of waste-water treatment technologies
References
* U.S. Environmental Protection Agency (EPA), Washington, D.C. (2013)
"Granular Activated Carbon."Drinking Water Treatability Database.
*
*
{{Wastewater
Water technology
Filters
Gas technologies